1. Field of the Invention
The present invention relates to a deflection yoke for a Braun tube and, more particularly, to a supplementary coil of a deflection yoke for a Braun tube which can form a magnetic field of a pin-cushion form at a screen part and a magnetic field of a barrel form at a neck part at the same time.
2. Discussion of the Related Art
FIG. 1 illustrates a section of a Braun tube schematically showing a mounting position of a conventional deflection yoke.
Referring to FIG. 1, the Braun tube includes a panel 1 forming a front face of the Braun tube and a funnel 2, a front portion of which is melt bonded to the panel 1. The funnel 2 has a convergent portion with a neck part 2a formed at an end thereof. An electron gun 4 is provided in the neck part 2a for emitting electron beams 3 toward the panel 1, and deflection yokes 7 are provided on an outer circumference of the funnel 2 for deflecting the electron beams 3 to predetermined spots. Red, green and blue fluorescent material layers 5 of dot or stripe forms are coated on inside surfaces of the panel 1, and a shadow mask 6 is spaced a predetermined distance apart from the fluorescent material layers 5 in an inner side of the panel 1. Numerous minute holes are provided in the shadow mask 6 for selective passing of the electron beams 3. Each of the electron beams 3 passed through the shadow mask 6 collides on the fluorescent material layers 5 to reproduce colors on the surface of the panel 1.
FIG. 2 is a perspective view of the conventional deflection yoke shown in FIG. 1.
Referring to FIG. 2, the deflection yoke 7 includes vertical deflection coils 9 for deflecting the electron beams 3 in a vertical direction, and horizontal deflection coils 8 (disposed on either side of the pusher part G) for deflecting the electron beams 3 in a horizontal direction, and a coil separator 10 for supporting the vertical and horizontal deflection coils 9 and 8, by acting as an insulator between the coils 9 and 8, and fixing a relative position between the funnel 2 and the vertical and horizontal deflection coils 9 and 8. The horizontal deflection coils 8 are, in most cases, wound in saddle forms and assembled into the coil separator 10, or wound in leading grooves(not shown) formed inside of the coil separator 10 for winding the horizontal deflection coils directly.
FIG. 3 illustrates a half section of the conventional coil separator 10 shown in FIG. 2, FIGS. 4A-4C illustrate different forms of magnetic fields each formed by the horizontal deflection coils wound on an inner circumferential surface of the coil separator 10 shown in FIG. 3, where FIG. 4A illustrates a barrel type magnetic field, FIG. 4B illustrates a pin cushion type magnetic field, and FIG. 4C illustrates a uniform magnetic field.
Referring to FIG. 3, of the deflection yokes 7, it is known that a neck part 10a with reference to a middle portion 10b of the coil separator 10 of the saddle type horizontal deflection coils 8 has an influence on convergence of the electron beams and a screen part 10c has an influence on distortions of the electron beams. The magnetic fields that the horizontal deflection coils 8 should form in each portion of the coil separator for an excellent convergence and prevention of distortions are shown in FIGS. 4A-4C. FIG. 4A illustrates a weak barrel type magnetic field 11, FIG. 4C illustrates a uniform magnetic field 12 in the neck part 10a shown in FIG. 3, and FIG. 4B illustrates a pin cushion type magnetic field 13 of an appropriate strength in the middle portion 10b shown in FIG. 3, or a strong pin cushion type magnetic field 13 in the screen part 10c shown in FIG. 3.
In order to form the foregoing magnetic fields, in winding coils from the neck part 10a to the middle portion 10b, either a supplementary coil(not shown) is wound at the inner screen part 10c or a groove is formed on middle of the coil for forming a coil distribution which has discontinuity in the continuous winding of coil between the neck part 10a and the middle portion 10b of the horizontal deflection coils 8. If appropriate magnetic fields can not be formed with the aforementioned winding, the winding pattern on which the coil is wound is either claded by welding or grinded before winding the coil to form a desired magnetic field.
In the meantime, in case of a slit type horizontal deflection coil(not shown), which is another form of the saddle type coil, the coil is wound along a groove formed in the coil separator to form a portion of the magnetic field between the neck part 10a to the screen part 10c in which the magnetic field has a sudden change.
However, the deflection yokes of saddle type or slit type horizontal deflection coils have the following problems.
In case of the saddle type horizontal deflection coil 8, since the coil can not be wound to pass many different portions with respect to angles in winding the coil from the neck part 10a to the screen part 10c, distribution of the winding can not be formed with variety. In order to adjust a portion of the winding distribution of the horizontal deflection coil 8, though pins are provided in the screen part 10c and the neck part 10a, distribution in the middle portion 10b with which a convergence can be greatly adjusted can not be adjusted without restraint.
Therefore, in case it is intended to produce a winding of a general saddle type coil 8 of a desired characteristic, separate additional measures, such measures as attachment of a helper(not shown) together with the supplementary coil, cladding by welding or grinding of the winding pattern for discontinuity of the pattern, or adjustment of the winding distribution by pusher, is required.
Though the slit type horizontal coil has an advantage in free adjustment of the winding distribution, it has a disadvantage of taking too much time in production.